1. Field of the Invention
The present invention relates to a control apparatus for a vehicle and a hybrid vehicle, and more particularly to control of an operation of an internal combustion engine in a hybrid vehicle incorporating the internal combustion engine and other source of drive power, the internal engine having an in-cylinder injector.
2. Description of the Background Art
There is known as one type of an internal combustion engine (engine) a configuration including an in-cylinder injector that directly injects fuel into a cylinder. As the in-cylinder injector experiences high temperatures in the combustion chamber, clogging tends to occur due to accumulation of deposits caused by the increased temperature at its tip. Such clogging of the injector may hinder normal fuel injection, and hence may invite fluctuations in the engine output. Accordingly, when there is a degree of freedom in use of the in-cylinder injector, care must be taken to avoid such clogging of the in-cylinder injector.
For example, Japanese Patent Laying-Open No. 2002-364409 (Patent Document 1) discloses an internal combustion engine that has both an intake manifold injector injecting fuel into an intake manifold and/or an intake port and an in-cylinder injector and that carries out an operation switching between homogeneous combustion and stratified charge combustion. Patent Document 1 discloses a configuration of carrying out fuel injection using both of the injectors during a homogeneous combustion operation to thereby address such a problem that the temperature of the in-cylinder injector (injector for direct injection) rises and deposits accumulate if the intake manifold injector (port injection) is solely operated in homogeneous combustion.
However, with the internal combustion engine having the configuration disclosed in Patent Document 1, it is still difficult to concurrently attain stabilization of a combustion state and suppression of deposits in the in-cylinder injector, in a partial load range such as a low-speed and high-load range.
Japanese Patent Laying-Open No. 2002-161841 (Patent Document 2) discloses a hybrid vehicle incorporating an internal combustion engine with an in-cylinder injector, and other driving force source of the vehicle such as a motor. Patent Document 2 discloses a configuration for suppressing carbon adhesion to a spark plug and for removing carbon adhered to the spark plug in such a hybrid vehicle. Specifically, when it is determined that the spark plug causes carbon fouling based on an operation state of the internal combustion engine, control is exerted to increase an electric load applied to the internal combustion engine by the motor-generator to thereby increase the temperature of the combustion chamber of the internal combustion engine to suppress occurrence of carbon fouling.
However, with the internal combustion engine having the configuration disclosed in Patent Document 2, while it is effective for suppressing carbon adhesion to and for removing carbon from the spark plug in the internal combustion engine of a hybrid vehicle, the increased temperature of the combustion chamber may increase the temperature of the in-cylinder injector at its tip to cause the injector clogging by the accumulated deposits.
Thus, in a hybrid vehicle incorporating an internal combustion engine with an in-cylinder injector and a motor and the like, it is necessary to control the operation of the internal combustion engine in order to prevent the temperature at the tip of the in-cylinder injector from becoming excessively high and inviting clogging due to deposit accumulation.